Liquid level indicator



.Fume i6, 1942, F. MCNEILL LIQUID LEVEL' INDICATOR 2 sheets-sheet 1Filed Feb. 14, 1938 6040250 We ree L. l l f l rm ma y www 8M r U o nef N[r F Y A @en 4 w M E M June 16, ma., F, MCEILL 2,286,919

LIQUID LEVEL INDICATOR Filed Feb. 14, 1938 2 sheets-sheet 2 ImventorFrederic M cNei/l Gttorlleg Patented `lune 16, 1942 LIQUID LEVELINDICATO-R Frederic McNeill, Chicago, Ill., assigner to T. W.

Ill.

McNeill Engineering Equipment C0., Chicago,

Application February 14, 1938, Serial No. 190,476

21 Claims. (Cl. 'T3-299) The present invention relates to liquid levelindicators and more particularly to liquid level indicators adapted toindicate the water level in boilers or the like at a point remote fromthe boiler.

The invention herein disclosed is in the nature of an improvement in theLiquid level indicator disclosed in my prior Patent No. 1,699,075.

One object of the invention is to generally improve liquid levelindicators of the type described.

Another object is to provide an indicator oi this type which isespecially adapted for floating vessels which, at times, tend to assumepositions other than horizontal. The present indicator is so constructedas to minimize the degree of error of indication under such conditions.

Another object of the invention is to simplify the installation ofindicators of this type and to provide for an improved arrangementwhereby the indicating means may be readily calibrated to insureaccuracy of indication. l

Another object of the invention is to provide for a retarding or dampingof the operation of indicating means so that the indicator will not beunduly influenced in sudden changesin level i of the boiler or otherreceptacle the level of liq uid in which is to be indicated.

Other and further important objects of the invention will becomeapparent from the disclosure of the specication and the accompanyingdraw ings.

In the drawings:

Fig. l is a schematic elevational View, partly in section, of a liquidlevel indicator made in accordance with one form of the invention;

Fig. 2 is an enlarged detail view of a portion of the device forproperly proportioning the volume of the Calibrating chamber;

Fig. 3 is a sectional detail View of one form of check valve used withthe device of the present invention;

Fig. 4 is a sectional detail View of a portion of a control chamberarranged to provide for retarding the indication of sudden changes inlevel of the liquid to be indicated; and

Fig. 5 is an elevational View, partly in section, of a modified form ofliquid level indicator.

The liquid level indicator, as herein disclosed, comprises an indicatingelement such as a glass tube containing two contrasting colorednonmiscible liquids, the line between the liquids being sharply definedand constituting the indicating line or level. The level of theindicating liquid is determined by the difference between the heads ofliquid in a constant head column and a varl means of pipes G, 6. y'umn 5is a standard water glass l.

While, for simplicity of description, the device ofy thepresent'invention has been described herein as'pertaining to boilers, itis desired that the term boilers be considered as being used in ageneric sense, as the present invention is applicable toA any artwherein it is desired to indi'cate at a distance the height of liquid ina liquid containing reservoir. It is also desired that reference towater be considered as used in a generic sense as lmeaning the liquid tobe measured. Y

The indicating device comprises a lower trap chamber casing Ii) and anupper trap chamber casing Il between which extends a transparentindicating tube I2 of glass or the like. The lower casing it isconnected to the lower end of the water column 5 by a conduit I3containing the variable head column and the upper casing lI is connectedto the upper end of the water column 5 by a conduit I4 containing theconstant head column.

The lower trap chamber casing is arrangedso that a column of heavyliquid I5, such as mercury, supports the variable head column conytainedin conduit I3 on one side and on the vuid I l not miscible with thecolored liquid, being ciliin the present` instance. Above the column ofoil I'l is supported a column of Water I8, assuming that water is theliquid to be measured. It is to be understood that, while the use ofcolored water is satisfactory, any expedient for obtaining a contrast inthe two contacting liquids in the indicating tube may be employed.

The amounts of oil Il, colored water I6, and mercury I5 in theindicating device are so re lated to the opposed heads of water columnsin conduit I3 and conduit Il! that a lowering of the head in conduit I3will cause a proportionate lowering of the level ci the upper portion ofthe Vcolored water column Ifi. By properly adjusting the capacity in thecompartments in the interior of trap chamber casing I the indication inthe glass tube I2 may be made closely correspondent or proportionate tothe changes in level of the water in the boiler.

A preferred construction of the lower trap chamber casing Il! will nowbe described. This casing is preferably tubular in form and is providedat the top with a plug 20 threaded into the top of the casing III. Thisplug is hollowed out to receive a packing member 2| which surrounds thelower end of glass tube I2. A packing nut 22 is provided to insure atight joint between the tube I2 and casing I0.

The casing I0 is preferably divided into primary and secondarycompartments 23 and 24 by means of a partition member Illa, preferablyof tubular form. These compartments communicate with each other at thelower end of the casing and constitute in effect a U-shaped compartmentor tube in which the legs are circular in shape and disposed inconcentric relation. The conduit I3 is connected to the casing I0 nearits upper end and communicates directly with the secondary or outercompartment. For this purpose, pipe I3a, forming part of conduit I3, isthreaded into the casing I0.

The trap chamber casing I0 is also provided with lling openings 25 and26 adapted to beV closed by packed plugs 21 and 28. The purpose oftheopern'ng 25 is to provide for controlling the introduction of asuitable quantity of mercury into the compartments 23 and 24; and thepurpose of opening 25 is to enable the outer compartment 24 to becompletely filled with liquid from the conduit I3. In this connection itis to be noted that the opening 25 is formed adjacent the upper end ofcompartment 24.

Means are preferably provided for fixing or proportioning the volumes ofthe primary and secondary compartments of casing I0. In the presentinstance this volume fixing means is located within the primary or innercompartment 23 and is preferably in the form of a pin-like element orcylinder 39 which may be termed a displacement or Calibrating member.

It is apparent that the larger the diameter of the Calibrating member3U, the smaller volume there will be left in the inner or primarycompartment 23 so that a proper selection of size of the Calibratingmember 30 is necessary to effect a control of the upward displacement ofcolored liquid in the indicating tube in accordance with the changes inlevel of water in the boiler. The construction must be such that whenthe high specific gravity liquid ows from, say, the outer compartmentinto the inner compartment, the volume of liquid entering the innercompartment will be controlled so that when an equal volume ofsuperposed liquid is displaced into the indicating glass the uppersurface of such liquid will properly indicate the level of water in theboiler. In practice, there will be required a particular size ofCalibrating member 30 for each indicating glass due to the fact thatthere is some slight degree of variation in the bore of indicatingglasses obtainable upon the market. Thus, by accurately measuring theinterior dimension of the indicating glass used in each instance, it ispossible to determine what degree in variation in size of theCalibrating member is necessary. This problem is a practical one and isreferred to herein for the sake of completeness of the description.

Another factor determining the size of the calibrating member 30 is thenormal difference in temperature existing between the water columns inconduits I3 and I4. If the upper part of the water column in the conduitI3 contains water under high steam pressure and consequently arelatively high temperature, it will be seen that this portion of thewater column, including the water in the boiler up to the level of thewater therein, Will be of less specic gravity than the equivalentportion of water in conduit I4. Thus an increase in height of the waterin the boiler, where such water is at a high temperature, will not causeso much displacement of the heavy liquid from the secondary to theprimary compartment as would be the case if the Water was cooler.Accordingly, the cross-sectional area of the member 30 must bedetermined so as to compensate for this difference in specific gravitybetween the water contained in the two conduits.

To explain this in more detail, if the water in the boiler is consideredas having a specific gravity of 1.00, it is obvious that the addition ofone .inch of water to the boiler would Cause the indicating fluid in theglass to move upward one inch under proper proportioning of the innerand outer compartments and indicating glass. Now, assuming that thewater in the boiler is subject to steam pressure under normal boileroperation, the specific gravity of the water in the boiler will be lessthan 1.00 and an increase of one inch of water in the boiler will notdisplace so much high specific gravity liquid from the outer compartmentto theinner compartment as in the previous example. Accordingly, inorder to assure the proper upward displacement of the indicating liquidin the glass, the inner compartment must be made larger with relation tothe outer compartment and in order to obtain this relationship a smallerCalibrating member 30 must be selected. The size of this member willtherefore depend upon the temperature at which a particular boiler is tobe operated.

Means are provided for preventing the escape of mercury or other heavyliquid from the inner compartment 23 in the event of breakage of thetube I2. For this purpose the plug 20 is formed with a concave undersurface 3| leading into the opening 32 which communicates with theinterior of the tube I2. The upper surface of the Calibrating member 30(see Fig. 2) is hollowed out at 33 to receive a valve member 34,preferably in the form of a metal ball capable of oating in the heavyliquid employed but not in the liquid thereabove. In the event the glasstube I2 should break, the ball 34 will remain in its seat 33 until theheavy liquid rises into contact with the ball whereupon the ball will becaused to rise with the upper surface of the heavy liquid and come torest at the lower end of opening 32 in the plug 20, thus preventing theheavy liquid from passing out of the primary compartment.

The Calibrating member 3Q is preferably held in place within the casingI0 by means of a plug 34, threaded centrally into the bottom wall of thecasing IIB. This plug 34 is provided with a threaded portion 35 on towhich the threaded lower end of the member 3B may b-e secured. A gasket3I of rubber or other suitable material may be disposed between thelower end of the member 30 and plug 34.

Means are preferably provided for withdrawing a desired quantity ofcolored uid I6 from the upper part of the compartment 23 withoutdisturbing the body of mercury therein. For this purpose the Calibratingmember 3d is provided with a duct 31 having an opening adjacent theupper end of the member and at the lower end thereof communicating withan opening 3B formed in the plug 34. The lower end of the opening 38 issuitably closed, as by means of a metal valve plug 4|). This valve plughas a slot 4| formed therein through the length of its thread so thatwhen open it will permit the passage of liquid through the conduits 31and 38.

In order to prevent the mercury from passing into the conduit 31, shouldthe mercury rise to a point near the upper end of the member 30, theupper end of conduit 31 terminates in downwardly inclined channels 42,42. Thus, before the mercury can begin to enter the conduit 31 it hascompletely closed branch conduits 42, 42 and the liquid trapped withinthe conduit 31 will prevent movement of mercury into it.

The preferred construction of the upper trap chamber casing will next bedescribed. This casing is provided with a screw-threaded plug 44disposed centrally in the top of the casing. The lower end of casing hasa threaded opening into which plug 45 is threaded. This plug is providedwith an opening 46 to receive a packing element 41 held in place by apacking nut 48 threaded exteriorly upon the lower end of plug 45. Theplug 45 is provided with a central opening to accommodate the tube |2.

The interior of casing is preferably divided into inner and outercompartments 5|! and 5|. For this purpose a partition member 52,preferably of tubular form is disposed within the casing II and held inplace by fitting it on an extension 53 formed on the plug 45.

The upper end of the partition member or casing 52 is tted with a plug54 provided with a centrally threaded opening 55 (see Fig. 4) into whicha retarding element in the form of a screw 56 may be disposed. Thethreads in the plug 54 are formed of a diiferent contour or depth fromthe threads on the retarding element or screw 56 whereby an opening willbe formed from the exterior to the interior of the inner casing 52around the threads. This opening is small and tends to resist the freepassage of fluid such as light oil between the interior and exterior ofcasing 52.

As will be more fully pointed out in the following description theopening through the plug 54 tends to retard movement of liquid betweeninner and outer casings 50- and 5| and prevents undue fluctuation of theindicating column, which would otherwise be likely to occur in a casewhere the boiler in which the liquid level was to be indicated waslocated on an ocean going vessel.

The lower end of casing has a threaded opening therein to receive a pipe|4a constituting the lower end of the conduit I4.

An opening 58 is provided, preferably about midway between top andbottom of the casing I I, to facilitate installation of the indicatingdevice as will be later more fully pointed out. This opening is providedwith a suitable closure, herein shown as plug 59.

The conduit I3 preferably extends from the lower end of water column 5to the upper end of trap chamber casing I0. As previously mentioned, thepipe |3a is joined to the casing I0. At the upper end of vpipe I3asubstantially in horizontal alignment with the point of maximumindication of the indicating fluid in glass I2 an opening |317 isprovided. This opening is closed by a plug |30. For convenience theopening |3b is provided by using an ordinary pipe T i3d.

The T |3d is preferably joined by a length of pipe I3e to another T |3fhaving an opening I3g closed by a plug |3h. A valve |31' is providedadjacent the T I3f. A pipe |31c connects the valve I3'i withanother T|3m having an opening |311 closed by a plug I3c. The other opening ofthe T I3m is connected to the water column 5 by means oi pipe |311controlled by a valve |3q.

The conduit I4 preferably extends from the lower part of trap chambercasing I I to the upper part of water column 5. Conduit I4 comprises apipe |40. joined to a fitting I4b having an opening |4c closed by a plug|4d. A valve |4e is provided approximately on the same level with thefitting |4b and between'the valve and fitting |4b is located a checkvalve |41'. See Fig. 3. This check valve will be later referred to morein detail. A pipe I4g leads from valve |4e to a chamber |4h which may betermed a capacity chamber. At the top of this chamber is provided afilling opening |4z' arranged to be closed by a plug |4lc. A pipe |4mextends between chamber |4h to the upper part of water column 5 and hasa valve |4'n located at the end thereof adjacent the Water column.

As shown in Fig. 3, the check valve I4f is preferably oi' the horizontaltype and comprises a main casing |4| of tubular form having pipes |42and |43 fitted in the ends thereof. The pipe |43 at its inner end isformed with a concave mouth |44 adapted to be closed by a ball |45. Inorder for the ball to close the opening it must be forced up theinclined surface of the concave opening |44. The pipe |42 is provided atits inner end with notches or openings |45 formed longitudinally thereofso that the flow of liquid toward the right, as view in Fig. 3, will notbe prevented.

A plug |41 is threaded into an opening at the top of casing |4| so as topermit ready replace ment of the ball |45.

The installation and operation of the liquid level indicating devicewill now be described.

After the liquid level indicating device has been installed inconnection with a boiler and the parts assembled substantially asindicated in,

Fig. l, the device in then ready to receive the various liquids to beused therein. A convenient procedure is to rst close valves I4n and |3q,as well as the valves |31 and |4e. Plugs I4lc and |30 are then removedand the pipes |376 and |4g cf the conduits I3 and I4 are then filled tooverflowing with water or whatever liquid is in the boiler or othercontainer being meas- Y ured.

It is to be noted thatthe water introduced into pipe |4g will remain inthe upper part of the conduit I4 only as high as will be permitted bypipe I4m and valve |4n. Thus, if the liquid to be measured is water in aboiler under steam pressure, it is apparent that the steam will pass outthrough valve |4n, when open, and through pipe |4m and will condense inthis pipe and in the capacity chamber |411.. The condensation willmaintain the liquid in the chamber I4h at a constant level as any excesswill constantly flow back through pipe I4m to the water column 5.

When the pipes i4g and |3lc are filled, as described, the plugs |4lc and|30 will then be replaced and valves I4n and |3q will be opened so thatwater in the water column 5 will flow out to join the water in the T I3mand so that the excess liquid in the chamber |4h may drain into .thewater Acolumn 5. At this point it is to be ob served that the head inthe Apipes I3lc and I4g is the same as it would normally be with nowater in the water column 5.

In order to continue to fill the indicating device, plugs |311, andlcinconduit I3 are removed and plug Md in conduitl I4 is removed; theplugs 44 and 59 and retarding screw 56 in the upper casing II areremoved and plugs .2'1 and 28 in the lower casing I are removed. Theplug 34 will be left in place and the needle valve 40 is maintainedclosed. Mercury is then preferably introduced into the lower casing IUby pouring it through the opening, normally closed by plug 44, andthrough the opening normally partially closed by retarding screw 56 inthe inner casing 52. The mercury passes down through the indicatingglass I2 and into the inner chamber1 23 .of the lower casing I9, thencerising in the outer chamber 24. Since the displaced air passes outthrough openings, such as openings 25 and 26, the two columns of mercurywill rise equally. Pouring of mercury continues until it begins to runout the opening 26. At this point no more mercury will be introduced andthe plug 23 will be replaced to close opening 26.

Water is then poured in through opening I3g until it overflows atopening 25 in the casing IU. Plug 21 is then replaced in such openingand the filling of conduit I3 continues until water overiiows at opening|31), which, as previously explained, is equal to the height of themaximum indication in glass I2. Needle valve 4|] is then opened andcolored indicating iiuid is poured in through the opening normallyclosed by plug 44 and through the opening normally partially closed byretarding screw 56 until it overflows at the needle valve by passinginto the passages 42 and 3l. The needle valve is then closed andadditional colored iiuid is added until the level of the iiuid is justeven with the bottom surface of the packing nut 48 connected with thecasing Il. In other words, the liquid is poured in un til the point ofmaximum indication is reached. At this point plug |30 is replaced inopening I3b. Water is then poured in through opening I4c until itoveriiows at opening 58, whereupon plug 59 is replaced to close thisopening.

The next step is to introduce oil into the inner chamber 5l) includingthe top portion Yof the indicating glass I2 and that portion of theouter chamber 5I not iilled with water. When the oil is filled to theopening closed by plug 44, both the retarding screw 56 and the plug 44are replaced. The oil used is preferably a fluent, transparent oil, suchas kerosene.

After the oil has been introduced, water will be poured in throughopening |39 and I4c vin conduits I3 and I4 until the water overflows atthese points, whereupon plugs I3h, and Md Will be replaced. It is to benoted that the conduits I3 and I4, as well as the upper and lowercasings I0 and II are now completely filled with liquid, no air or othergas being present except in the upper part of chamber Mh and pipe 14mand possibly in conduit 31 in trap chamber casing IU.

Valves I3z` and I4@ are then opened and, if the water column 5 is empty,or at minimum level, the colored iiuid in the indicating glass I2 willrecede to substantially the point of zero indication. The reason it doesnot go entirely to the zero point is due to the fact that the foregoingmethod of lling causes a greater amount of indicating fluid to be put inthan that required to compensate for the diiTerence in thelength of theconnecting pipes I3k and |49. Assuming that the Water in water column 5is at the minimum level, 'the excess indicating vfluid is then drained`out through the needle Valve 40 to the point oizero indication. If thewater column is partly full it will only be necessary to drain outexcess colored'iiuid to a point where the indication in glass ,I 2 givesthesame indication as that in glass I on the water column. During theoperation of drawing off the excess colored iiuid any airtrapped inconduit 3l will escape.

During the operation of this form of the invention any change in levelof the Water in the boiler will create a greater or less difference inhead between the water in conduits I3 and I4. The .constanthead conduitwill `remain constant in the present instance by reason or" condensationoccurring in pipe I4m which keeps the surface of the liquid in chamberI4h at substantially a constantlevel. In the.event that the body ofliquid in conduit I4should rise it is apparent that the excess will flowback .along the vpipe I4m to the .watervcolumn 5.

Assuming, for example, .that the boiler is operating under steampressure, it is to be observed thatan equal pressure Will be imposed onthe upper surface of each .column of liquid in conduits I3 and I4.Accordingly, the difference in head between the two Vcolumns of liquidwill 4be the only variable factor .tending to change the level ofindicating `iiuid in the tube I2. As the surface of the water in theboiler gets lower the level `of indicating fluid Vin the tube I2 willsink proportionately. The reason for this is, as previously stated, thatthe mercury in the lower part of the trapvchamber II) will begin to flowfrom the inner compartment 23 to the outer compartment 24 so that thedifference in head between the two columns of mercury will just balancethe diierence in head of the water .columns. Due to the Vmanner ofdetermining the -relative sizes of the inner and outer compartmentsofthe trap chamber, the indicating fluid will move downwardsubstantially exactly in accordance with the downward movement of thewater in the water column 5, as indicated by `gauge glass l.

When the water in the boiler is replenished just the opposite actionoccurs as will be readily understood.

Due to the provisionof the retarding element 55 inthe upper trap chamberthe displacement of liquid between the inner and outer compartments and5I will be retarded. 'I'hus when the device of the present invention isused on ships and other' mobile structures, subject at times to quickperiodic changes-in level or angu-a lar position with reference to thehorizontal, there will be no sudden change in the level of theindicating liquid andthe tendency will be to cause the indicator toremain substantially constant.

In the event of breakage of the indicating tube I2 when the boilerI isoperating under pressure the check valve yI4J wil immediately close dueto the pressure in the conduit I4. At the same time the pressure inconduit I3 will cause the metal ball in lower trap chamber Iii to riseand close the lower end of the duct 32. The usual kresult on breaking ofthe tube I2 is an instan- 4with appreciable speed. The water in theupper part ofthe trap chamber Il) would begin to flow out and this wouldcontinue until the metal ball 34 was floated by. the mercury intoposition to close the duct 32, after which the flow would stop and nomercury would be lost.

In the event of a slow leak occurring in either conduit I3 or conduit I4the mercury column will rise either in the tube I2 or in the lower partof the conduit I3, depending upon the point of leakage, and this risingmovement will continue until the weight of the mercury, as for example,in the tube I 2, together with such amount of liquid as shall remainthereabove, will balance the weight of the column of water and mercurylocated in the lower end of conduit I3 and the lower end of the trapchamber IG.

The lengths of the inner compartment 23 and the outer compartment 24 andthe cross sectional areas thereof, considered with the cross sectionalarea of the tube I2, are preferably such that a column of mercury in theinner compartment 23 and the tube I2 will balance the remaining mercuryin the outer compartment 24 and the water in the conduit I3 before allof the mercury is expelled from the outer compartment. In other wordsthe parts are so related that before the water in conduit I3 will passdown into the compartment 24 and thence into the compartment 23 whichwould cause the water to begin to flow up through the body of mercury,the body of mercury in the inner compartment 23 and the tube I2 togetherwith the liquid above the mercury will balance the weight of liquidincluding both mercury and water in the compartment 24 and the conduitI3.

The above mentioned relationship is also useful if for some reason theconduit I4 is not properly lled with water at the beginning of theoperation of the device.

If a slow leak occurs in the conduit I3 the reverse operation ensues,namely, the mercury will begin to rise in the conduit I3 and willcontinue rising until the column of mercury in the conduit I3 willbalance the weight of the water in conduit I4 and in the lower end ofthe inner compartment 23 and this balancing result will occur before themercury will become entirely displaced from the inner compartment 23.

In referring to the operation lof the device due to a leakage in conduitI3 or conduit I4 it may be assumed that the metal ball in the upper partof trap chamber I0 is either not present or is not operative tocompletely close the lower end oi the duct 32.

The lengths and the cross sectional areas of the upper trap chambercompartments 5H and El are so related to the cross-sectional area of thetube I2 that when a leak occurs in conduit I3, causing the mercury torise in this conduit and lower in the tube I2 with a consequent loweringof the body of the oil in tube I2 andinner compartment Sii, and causingthe water to rise in the outer compartment 5I, the movement of thecolumn of mercury will stop before the `oil has completely flowed fromthe outer compartment 5|, which would tend to permit water from conduitit to flow into the inner compartment. If a leak should occur in theupper part of conduit I5 the mercury, as previously indicated, will risein tube I2 until the column of mercury in this tube will balance theweight of the water as above described in conduit I3. Since the upwardmovement of the mercury column will cease before the lower end of thecolumn passes beyond the outer compartment 24 and into the innercompartment 23, the flow ofoil will accordingly also cease before theoil has passed from the outer compartment 5| of the upper trap chamberinto the conduit I4. From the above it is apparent that no oil willbecome lost from the trap chamber due to leakage in conduits I3 or I4.

It is also to be noted that the colored liquid I6 during any extremeuctuation in the body of the mercury in the lower trap chamber and thebody of oil in the upper trap chamber, will remain either in the innercompartment 23 of the lower trap chamber, as for example, when thecolumn of mercury is moving into the conduit I3; or the colored uid I6will be retained entirely in the tube I2 and in the inner cornpartment53 of the upper trap chamber, as for example, when the mercury is movingup into the tube I2 in order to balance the column of water in theconduit I3.

It is to be further noted from the foregoing that the various liquids,namely the mercury, colored fluid, and the oil contained respectively inthe lower trap chamber, in the tube I2, and the upper trap chamber willalways be maintained in their original relative positions during normaloperation of the device as well as during certain abnormal operations,such as leakages occurring in the conduit I3 and conduit I4.

It is also to be noted that any foreign matter such as scale or othersediment that may be carried over into the conduit I4 will be retainedin the lower end of the upper trap chamber and thereby prevented fromreaching the liquid in the tube where it would interfere with theindicating function of the tube.

When it is desired to install a new tube I2 to replace a broken one thevalves I3i and I4e are closed to cut ol pressure to the indicatingdevice. The broken parts are removed after which plugs 44 and 54 areremoved and packing elements 22 and 48 suitably removed or loosened. A-new glass can then be inserted downwardly through the upper trap chamberuntil it assumes the position indicated in Fig. 1. The upper and lowerpacking elements will then be tightened whereupon the device is readyfor recharging with the necessary liquids by repeating part of the stepsoutlined above. After the liquids have been introduced the plugs 54 and44 are replaced and the device is then ready for continued operation.

The modified form of the invention, illustrated in Fig. 5, will now bedescribed. In this form of the invention the indication is given by thesame liquid that is used to balance the difference between the heads ofwater in the variable head column and the constant head column. In thisform the water column indicated at 235, is ccnnected to a boiler orother receptacle by pipes 206, 2M and carries anindicating glass 201.

The indicating device, as disclosed in this mod.. ified form of theinvention, comprises a lower trap chamber casing 2I0 and an upper trapchamber casing 2| I between which extends the transparent indicatingtube 2I2 of material, such as glass. The lower casing 2 I 0 is connectedto the lower end of the water column 235 by a conduit 2|3 and the uppercasing 2| I is connected to the upper end of water column 205 by aconduit 2 I4.

The lower trap chamber casing is arranged so that a column 2| 5 ofliquid of high specific gravity, preferably a liquid of the type ofacetylene tetrabromide, lls same and extends upwardly into both the tube2| 2 and the conduit 2|3. The high specific gravity liquid employed isnonmiscible with the water or other liquid to be measured and ispreferably readily adapted to be permanently colored so as to be clearlydistinguishable from the liquid to be measured.

The water'218, or other liquid to be measured, lls the conduits 213 and214 andis in contact with both branches or columns of the high specificgravity liquid.

The amount of high specific gravity liquid 215 is so related to theopposed heads of water columns in the conduits 213 and 214 that alowering of the head in conduit 213 will cause a proportionate loweringof the level of the upper surface of the liquid 215 in the glass 212. Byproperly adjusting or altering the specific gravity of the liquid 215 itis possible to obtain an indication in the glass 212 which will changeina substantially identical manner with the changes of vwater level in theboiler.

The lower trap chamber 211] may be formed in a manner generally similarto the trap chamber I1) of the form of invention rst described. Thiscasing is preferably tubular and is provided at the top with suitablyconnecting. fittings, indicated generally at 220, enabling. the glass 2I 2 to be connected to the casing 210 in a liquid tight manner.

An inner casing member or partition221, in the form of an open endedtube, is secured at the top of the casing 210 and has its lower enddisposed adjacent to but spaced from the lower wall of this casing. Aplug 234 is arranged to close a drainage opening in the lower wall ofthe casing 211). This plug 234 is preferably provided with a needlevalve member 240 to enable selected quantitiesof the liquid 215 to bewithdrawn. The same general form of lower trap chamber casing may beused in this form of the inventionas in the rst described form exceptthat the equivalent Vof. the Calibrating member 3Q may be dispensedwith.

The conduit 213 is suitably connected toV thel trap chamber 215,preferably, as indicated, at a point near the top of the casing. Thisconduit comprises a section of' pipe 2 I3aconnected at the point justmentioned and extending upward to a height approximately equal to thatof the point of maximum indication in the glass 212. At its upper endthe pipe 2I3a is connected with a tting in the form of a closedreservoir 2 13b having a horizontal cross-sectional area substantiallygreater than the corresponding area of the pipe 2I3a. This reservoir hasan opening closed by a plug 213e.

A pipe 213e extends upwardly from reservoir 213D, and' is connected witha fitting 213] having a filling opening therein closedby a plug 213g. Apipe 213k connects fitting 2I3f with a check valve 213i which in turn isconnected to a valve 213i. This valve is connected through pipe 213k t afitting 213m providedwith a plug 2 |371., Fitting 215m is connected bypipe 21370 to a valve 21311 connected to the water column 285 at itslower end.

Check valve 213i is similar to check valve 14j of the form firstdescribed and is arranged to stop the flow of water or steam throughconduit 213 toward the glass 212 in the event the latter should becomebroken.

The upper trap chamber casing 211, as in the case of' casing 2111, maybe formed generally similar to the upper trap chamber casing 1I in therst described form of the invention. This casing 21 1 is preferablytubular and is provided with a screw-threaded plug 244 closing anopening in the top wall of the casing. 'Ihe bottom of casing 211 isprovided with suitable fittings, indicated generally at 245, enablingthe glass 212 to be connected to the-casing 211 inY a liquid tightmanner. Y

An inner casing or partition 252, in the form of an open ended-tube, issecured at the lower end of'casing 21 I and has its upper enddisposed'adjacent but spaced from the upper end of the casing.

The upper end of the partition member or casing 252 is fitted with aplug 254 provided with a centrally threaded opening into which athreaded closure member 256 may be disposed. The threads in the plug254, as in the first form of the invention, are formed of a differentcontour orv depth from the threads on the closure member 256 whereby anopening will be formed from the exterior tothe interior of the innercasing 252 around the threads. 'I'his opening is small andv tends toresist the free passage of uid between the interior and exterior ofcasing 252.

A pipe 2I4a, constituting the lower end of conduit 214, is preferablyconnected to the lower end of the casing 2-11. This pipe extends upwardand terminates in a fitting 21417, having a filling opening closed by aplug 214d. A valve 214e is provided approximately on the same level withthe fitting 2 14d and between the valve and fitting is located a checkvalve 2141. This check valve is similar to check valve I4f of the formfirst described. A pipe 214g leads from valve 214e to a chamber 214hwhich may be termed a capacity chamber. At the top of this chamber isprovided a filling opening arranged to be closed by a plug 214k. A pipe214m extends between chamber 214h to the upper part of water column 205and has a valve 2I4n located at the end thereof adjacent the watercolumn.

The installation and operation of the device constituting this modifiedform of the invention will now be described.

With the system connected, as shown, the valves 2137', 21311, 214e and2141i will be closed and plugs 213C, 213g, 21311, 214d, 214k and 244 andretarding screw 256 removed from the openings which they close. Highspecific gravity liquid, such as acetylene tetrabromide, will then bepoured in at the opening closed by plug 244 until the casing 210has-become lled, as well as tube 212, to the point of maximumindication. At this point the liquid will start to flow out of theopening in casing 2131), and this casing will then preferably be abouthalf full.

Plug 213C will thenA be replaced whereupon clear water, or if desired,distilled water 218e is poured into the opening in tting 2I4d to fillthe inner and outer compartment of the upper trap chamber 211 and alsoto ll the fitting 2I4d, and the valve 2141 up to the valve v214e whichis maintained closed during this portion of the filling, Ordinarilyboiler water is then poured in the opening of the fitting 2131 until itoverflows at the opening whereupon the plug 213g and the plug 21411 arereplaced, The retarding screw 256 and plug 244 will also then bereplaced, whereupon water is poured into plug openings 2131i and 214kuntil it overflows into pipe 214m out of the casing of fitting 214h andout ofthe casing 213m into pipe 21312. During this operation valves 213qand 2141i are re tained closed. The plugs 21311I and 214k are thenreplaced. The valves 213g and 214n are then opened and the indicatingdevice is then ready for operation.

Upon opening valve 21411, any excess water in the conduit 214 will owback along the pipe 2Mb and will run into the water column 205, thenormal level of liquid remaining in the conduit 2M may be convenientlyreferred to as the constant head level or the level of the constant headcolumn.

Steam passing out along pipe 2mm will condense and maintain the water incolumn 2|4 at a constant level. If the level of water in the watercolumn 205 is at maximum the top of the column of high speciiic gravityliquid 2|5 will remain at its maximum indication. As the water in thewater column 205 recedes, due to lowering of the level in the boiler,the level of liquid 'H5 in the glass 2l2 will recede so that thedifference in head of the two opposed columns of liquid 2l5 will justequal the difference in head between the two water columns.

The manner of obtaining movement of the liquid 2l5 in the indicatingglass 212 substantially exactly with the changes in water level in thewater column 205 will now be described. For this purpose the speciiicgravity of the water in the boiler is determined. In this connection, itmay be stated that different boilers may be adapted to operate atdierent pressures and temperatures, hence there will be a difference inthe specic gravity of boiler water between one boiler and another. Inorder to adapt the device to a particular boiler the specific gravity ofthe liquid 2l5 will be altered by the addition of some readily misciblefluid which also has the property of being nonmiscible with water. Thus,when acetylene tetrabromide is used as the high specific gravity liquid,its specic gravity may be varied by the addition of oil, or othersuitable lighter liquid.

If, for example, it is desired to indicate variations of level of waterin the boiler the temperature of which would cause the water in theboiler and in the upper part of the constant head liquid column to havea specific gravity of .80, and assuming that the total variation to bemeasured was ten inches, the variable and constant head columns would beconnected to the water column 205 at a distance of ten inches betweencenters, that is, the distance would be measured between the centers ofpipes 21311 and 2I4m.

As thev indicating panel will ordinarily be placed Vat a point remotefrom the boiler where the temperature is substantially that of ordinaryroom temperature, the water in the water columns adjacent the indicatingapparatus can be considered as having a specific gravity ofsubstantially 1.00. The water at the top of the constant head column,being in direct contact with steam from the boiler, will have atemperature generally corresponding with that of the steam and a limitedportion of the upper part of the constant head column will thereforecontain water which is of a lower specific gravity. The same thing istrue with regard to the variable head column up to the point where thiscolumn joins with the water column 205 of the boiler. The temperature ofthe water will gradually decrease for points more and more remote fromthe upper ends of both conduits until the ternperature reachessubstantially that of ordinary room temperature. As substantially thesame comparative condition exists in each conduit, the respective headsof water in each of the conduits will balance out against each other sothat, for practical purposes, it is only necessary to deal with thatportion of the body of Water in the boiler above the point of minimumlevel to be measured, that is, above the upper end of the conduit i3. i

As, in the example above given, the specic gravity of the liquid to bemeasured is .80 it is apparent that a difference of 10 inches in levelof the water in the boiler will be equivalent to only an 8 inchdifference in head of water at specific gravity of 1.00. The highspecific gravity liquid in the gauge must then have its specic gravityso altered as to cause its upper level in the indicating tube to moveone inch for every inch of change in level of the water in the boiler.In order to determine the proper specic gravity of the high specificgravity liquid, let it be assumed, for the moment, that the horizontalcross-sectional area of the casing 2I3b is innnitely large. Under such acondition the level of the high specific gravity liquid 2|5 in thiscasing would not change with iuctuation in the boiler level and all ofthe change would occur in the surface of the liquid 2l5 in the tube 2I2.Under such a condition the specific gravity of the liquid 2 I 5 must befixed at 1.80, the specific gravity being changed by mixing it with oil,or other suitable lighter liquid, as explained above. Thus it isapparent that a difference of ten inches between the level of theconstant head conduit and the level of the variable conduit will equal ahead of eight inches of Water (of specific gravity of 1.00) assuming, asabove, that the water being measured has a speciiic gravity of .80. Thusthe diierence in head between that portion of the water in the tube 2I2extending from the upper surface of liquid 2l5 to the point of maximumindication on the one hand, and the portion of liquid 2I5 in conduit 2I3between these same levels is 8, thus, balancing the head difference of 8between the upper ends of the variable head and constant head conduits.

Since the casing 2I3b does not have an innite area there will be aslight change in level of the liquid 2I5 in this casing as the level ofwater changes in the boiler. The specific gravity of the liquid ZIE musttherefore be altered so as to compensate for the slight rise and fall oflevel in the casing 2|3b. In other words, the specific gravity of theliquid 2 l5 must be slightly less than 1.80. For example, if thecross-Sectional areas of the tube 2l2 and casing 2I3b, are in the rationof l to l0, the level of liquid 2I5 in casing 2 I3b would change l inchfor 10 inches of change in the level of liquid in tube 2I2. The dierencein height between the two opposed surfaces of liquid 2|5 in the tube 2I2and conduit 2 I3 would be 11 inches. Thus, a head diierence in the twoconduits equal to 8 would have to be translated into 1l inches ofmovement between the upper surfaces of liquid 2 l5. In practice, therelationship of the parts would produce a change in level of liquid incasing 2|3b` of approximately ,-g inch with ten inches of movement ofthe liquid 2|5 in tube 2l2.

The formula for determining the proper specific gravity of the liquidZIE may be developed as follows. Let X represent the specific gravity ofthe heavy liquid. Let L1 represent the diierence in height between thetwo columns of high specific gravity liquid. Then, since the head may becomputed by multiplying the height of the liquid by its specificgravity, the head of column L1 may be represented as LlX. Let Wlrepresent the head of liquid to be measured, that is the liquid inconduit 2|@ which is above the level of liquid in conduit 2 I3. Then letW2 represent the head of theA liquid in the indicating glass just abovethe top of the liquid 215'. The leng-th of this column of liquid willequal the length of the column Ll in the conduit 213. The formula maythus be written- As assumed above, the length of L1 is 11 inches; thelength of the head of water W2 must also be 11 inches; and the length ofthe head of water W1 is 10 inches. As the specific gravity of the waterin Wl is assumed to be .80, the head W1 will be represented by 8.00. Asthe specific gravity of the head of water W2 is 1.00, the head W2 may berepresented by 11. The head of heavy liquid L1 may be represented as11X. The equation may then be written- X=19/l1=1.727 (specic gravityofthe heavy liquid 215) In the form of invention illustrated in Fig. 5,if the indicating tube 212 should become broken while the boiler isoperating under pressure, the water in both conduits 213 and 214 wouldbegin to iiow toward the indicating tube. This now of water, however,would immediately be stopped by the operation of the check valves2l3iand 214]. Should a leak occur while the boiler is not operatingunder pressure, either in conduit 213 or 214 the liquid 215 will rise ineither the tube 212 or the conduit 213 until the difference in headbetween the two branches of the high speciiic gravity liquid is suicientto cause the short branch and the column of water in the conduitunaffected by a leak to be balanced by the longer branch of the highspecic gravity liquid. The sizes of the trap chambers and the tube 212are such that the high specific gravity liquid will not pass completelyout of the inner compartment oi the lower trap chamber and up into theconduit 213, or in the reverse direction, this liquid will not pass upinto the tube 212 and into the upper trap chamber to such an extent thatthe lower end of the liquid will pass completely out of the outercompartment of the lower trap chamber 21%.

From the foregoing it is apparent that the liquid level indicator of thepresent invention may be readily adapted for indicating at a remotepoint the level of water in boilers or the level of other types ofliquids in closed receptacles. The instrument board of the indicatingdevice may be placed at any convenient point below the level of theliquid in the container to which the indicating device is attached. By aproper adjustment of the cooperating parts and the specic gravity of thebalancing liquid in the indicating device, it is possible to registerindications which are substantially identical with the indication givenby an ordinary gauge glass` attached to the boiler at the water level.

While the present description sets forth certain preferred embodimentsof the invention, numerous changes may be made in the constructionillustrated without departing from the spirit of the invention, and itis therefore desired that the present embodiments be considered in allrespects as illustrative and not restrictive, reference being had to theappended claims rather than to the foregoing description to indicate thescope of the invention.

I claim:

l. A remote liquid level indicator of the type in which three superposedcolumns of nonmiscible liquids each diiering in specific gravity areinfluenced by water containedin. water conduits connected respectivelyto a boiler beyond points of normal maximum and minimum levels, saidindicator comprising in combination, a transparent indicating tubecontaining superposed columns of colored water and oil, a pair of trapchamber casings spaced apart and connected respectively at the upper andlower ends of the indicating tube, said trap chamber casings beingindependent of each other whereby the central portion of the indicatingtube is left in an unobstructed condition, the lower trap chambercontaining a column of mercury beneath the water and oil columns, theupper trap chamber casing having a partition member therein dividing thechamber into two concentric compartments, the inner compartmentcommunicating directly with the indicating tube, the partitionseparating the inner and outer compartments of said upper trap chamberhaving an opening therethrough in an upper portion thereof to providecommunication between said compartments, and means removably disposed insaid partition opening for restricting the same thereby to retard thefree itiow of liquid from one compartmentl to the other.

2. A remote liquid level indicator of the type in which three superposedcolumns of nonmiscible liquids each differing from the others in itsspeciiic gravity are influenced by water contained in water conduitsconnected respectively to a boiler beyondv points of normal maximum andminimum levels, said indicator comprising in combination, a transparentindicating tube containing superposed columns of colored-water and oil,a pair of trap chamber casings spaced apart and connected respectivelyat the upper and lower ends of the indicating tube, said trap chambercasings being independent of each other whereby the central portion ofthe indicating tube is left in an unobstructed condition, the lower trapchamber containing a column of mercury beneath the water and oilcolumns, the upper trap chamber casing having a partition member thereindividing the chamber into two vertically extending compartments, onecompartment communicating directly with the indicating tube, there beingan opening in the partition member between the compartments and locatedadjacenrt to the upper portions thereof, and means removably disposed insaid partition opening for restricting the same thereby to retard thefree iiow of liquid from one compartment to the other.

3. In a liquid level indicator a trap chamber casing having an indicatorglass, said trap chamber casing having vertically disposed inner andouter conccntrically related chambers, the inner chamber being adaptedfor directed connection with the indicating glass, a body of light oilnormally contained in the upper portion ofY both inner and outerchambers, a body of water contained in the lower portion of the outerchamber, the inner chamber being separated from the outer chamber by awall having an opening therein, a closure element secured within saidopening, there being a small space provided between the wall openingandthe closure element whereby a restricted passage is provided betweenthe two trap chambers when the closure is in place, the body of the oilwithin the upper portion of both trap chambers being positioned toprevent the water in the lower portion of the outer chamber fromentering and passing through the said restricted passage.

4. In a liquid level indicator a trap chamber casing having an indicatorglass, said trap chamber casing having vertically disposed inner andouter concentrically related chambers, the inner chamber being adaptedior direct connection with the indicating glass, a body of light oilcontained in the upper portion of both inner and outer chambers, a bodyof water contained in the lower portion of the outer chamber, the innerchamber being separated from the outer chamber by a wall having athreaded opening therein, a threaded closure element adapted to besecured within said opening, the threads oi the closure element beingloosely related to the threads of the opening whereby a restrictedpassage is pro-- vided between the two trap chambers, the body of theoil within the upper portion of both trap chambers being positionednormally to prevent the water in the lower portion of the outer chamberfrom entering and passing through the said restricted passage.

5. In a liquid level indicator a trap chamber casing having an indicatorglass, said trap casment secured within said opening, there being a J..

small space provided between the wall opening and the closure elementwhereby a restricted passage is provided between the two trap chamberswhen the closure is in place, the body of the oil within the upperportion of both trap chamber casings being positioned to prevent thewater in the lower portion of the outer chamber from entering andpassing through the said restricted passage, the trap chamber casinghaving an opening in an outer wall adjacent to the closure element forthe wall of the inner chamber giving access to such closure element, anda second closure element for closing the opening in the outer wall.

6. In a liquid level indicator, a trap chamber f casing, a partition inthe casing separating it into primary and secondary chambers, therebeing a passage providing intercommunication between lower portions ofsaid chambers, the primary chamber being arranged for connection with anindicating tube, the secondary chamber being arranged for connectionwith a water conduit adapted to cause head pressure in the conduit to beimposed on the trap chamber, said trap chamber casing being adapted tocontain a body of heavy liquid extending into both the primary andsecondary chambers and adapted to contain a body of lighter liquid,nonmiscible with the heavier liquid, disposed in the primary chamber,means for 'withdrawing a portion of the lighter liquid from the primarychamber, said means comprising a member in the primary chamber joined toa wall of the trap casing and extending a substantial distance above thenormal level of the heavy liquid therein, l said member beine formedwith a duct extending therethrough and to the exterior of the trapchamber casing, and means for closing said duct.

'7. A liquid level indicator comprising, a vertically disposed trapchamber casing, a partition in the trap chamber casing separating itinto primary and secondary chambers, there being a passage providingintercommunication between lower portions of said chambers, the primarychamber having an outlet at its upper end and being provided with meansat the outlet for connection with an indicating tube, the secondarychamber being arranged for connection with a water conduit adapted tocause head pressure in the oonduit to be imposed on the trap chambers,said trap chamber casing being adapted to contain a body of heavy liquidextending into both the primary and secondary chambers and adapted tocontain a body of lighter liquid, nonmiscible with the heavier liquid,disposed in the primary chamber above the heavier liquid, a Calibratingmember for the primary chamber comprising a pin-like element securedwithin the primary chamber and having its upper end in close proximitywith the outlet leading to the indicating tube connection, and a checkvalve element supported on the upper end of the pin-like element, saidcheck valve elementbeing floatable in the heavy liquid but not floatablein the lighter liquid whereby a rise in level of the heavy liquid willfloat the check valve element into position to close the outlet leadingto the indicating tube connection and prevent the heavy liquid fromowing through such outlet.

8. A liquid level indicator comprising, a vertically disposed casing, achamber formed in the casing, the casing being provided with an openingfor connecting the chamber with an indicating tube, means for causing ahead pressure to be imposed on the chamber, said chamber being adaptedto contain a body of heavy liquid partially filling the chamber andadapted to contain a body of lighter liquid, nonmiscible with theheavier liquid, disposed in the chamber above the heavy liquid, meansfor withdrawing a portion of the lighter liquid from the chamber, saidmeans comprising a pin-like element in the chamber joined to a wall ofthe casing and extending a substantial distance above the normal levelof the heavy liquid in the chamber, said element being formed with aclosable duct extending therethrough and through an opening formed inthe wall of the casing, said duct being formed with a verticallyextended bore terminating short ofthe upper end of the pin-like elementand a connecting bore extending downwardly from the vertically extendedbore to the exterior of the pin-like element, the duct opening on theexterior of the pin-like element being entirely below the point ofconnection of the downwardlyextending duct and the vertically extendingduct, whereby niiow of heavy liquid into the duct, in the'event of arise in level of the heavy liquid above the opening of the duct, will beprevented due to trapping of the lighter liquid in the duct.

.9. A liquid level indicator comprising, a trap chamber casing, apartition in the trap chamber separating it into primary and secondarychambers, there being a passage providing intercommunication betweenlower portions of said chambers, the primary chamber being arranged forconnection with an indicating tube, the second ary chamber beingarranged for connection with a water conduit adapted to cause headpressure in the conduit to be imposed on the trap chambers, said trapchamber casing being adapted to contain a body of heavy liquid extendinginto both the primary and secondary chambers and adapted to contain abody of lighter liquid, nonmiscible with the heavier liquid, disposed inthe primary chamber, means for withdrawing a portion of the lighterliquid from the primary chamber, said means comprising a pin-likeelement in the primary chamber functioning to properly proportion thevolume of the primary chamber with that of the secondary chamber, saidcasing having an opening in its lower end, a plug arranged to beremovably secured within said opening, means for securing said pin-likeelement to the inwardly directed portion of the plug, said pin-likeelement and plug being formed with registering ducts extendingtherethrough, and means on the outer portion of the plug for closing theduct therein.

10. A remote liquid level indicator of the type in which two superposedcolumns of nonmiscible liquids, each differing in specic gravity, areinuenced by water contained in water conduits connected respectivelyabove and below the points of normal maximum and minimum levels, saidindicator comprising, in combination, a transparent indicating tube, avertically disposed trap chamber casing having primary and secondarychambers communicating with each other at their lower ends, theindicating tube being directly connected to the upper end of the primarychamber, a water conduit connected to the upper end of the secondarychamber, said water conduit extending vertically above the point ofmaximum indication to be given by the indicating tub-e, a body of highspecific gravity liquid partially llling the primary and secondarychambers, said water conduit being provided with a controllable openingat the level of maximum indication of the indicating tube, whereby,after said conduit has been lled, with liquid to be measured, up to theopening in said conduit, the desired amount of indicating fluid, havingthe same specific gravity as the liquid to be measured, may beintroduced into the indicating tube and primary chamber due to theoutiiow of liquid to be measured through the conduit opening, suchamount of indicating iluid being indicated as suflicient when the levelof the iluid reaches the point of maximum indication, an indicatingfluid in the said indicating tube and floating in the upper portion ofsaid primary chamber upon said highV specific gravity liquid, and meansfor bleeding out from said primary chamber, without disturbing said highspecific gravity liquid, any excess quantity of the indicating iluid forthe purpose described.

11. In a device of the character described, an upper hollow trap member,means separating the interior of said upper trap member into inner andouter communicating chambers, said upper trap member having a topopening to the outer chamber and removable means closing the opening,said upper trap separating means having a top opening substantially inaxial alignment with the top opening on the upper trap member, saidupper trap member inner chamber also having a bottom openingsubstantially in axial alignment with its top opening, a lower hollowtrap member disposed at a relatively iixed distance from the upper trapmember, means separating the lower trap member into inner and outercommunicating chambers, said lower trap member having a top opening toits inner chamber and in axial alignment with the said bottom opening inthe upper trap member, and a tubular sight glass extending between saidupper and lower trap members and through its respective endsestablishing communication between the inner chambers of the upper andlower trap members respectively through the bottom and top openingsthereof, said sight glass being insertable and removable through the topopenings of said upper trap member and the said separating means in theupper trap member.

l2. In a device of the character described, an upper hollow trap member,means separating the interior oi said upper trap member into inner andouter communicating chambers, said upper trap member having a topopening to the outer chamber and removable means closing the opening,said upper trap separating means having a top opening substantially inaxial alignment with the top opening in the upper trap member, saidupper trap member inner chamber also having a bottom openingsubstantially in axial alignment with its top opening, a lower hollowtrap member disposed at a relatively xed distance from the upper trapmember, means separating the lower trap member into inner and outerchambers communicating with one another at their lower ends, said lowertrap member having a top opening to its inner chamber and in axialalignment with the said bottom opening in the upper trap member, atubular sightl glass extending between said upper and lower trap membersand through its respective ends establishing communication between theinner chambers of the upper and lower trap members respectively throughthe bottom and top openings thereof, said sight glass being insertableand removable thrcugh the top openings of said upper trap member and thesaid separating means in the upper trap member, said lower trap memberhaving a bottom opening leading to said lower trap member inner chamber,a displacement member removably disposed in said bottom opening of thelower trap member, and a valve normally supported on said displacementmember and adapted to float upwardly, upon liquid rising in said innerchamber of the lower trap member, to close the top opening in said lowertrap member thereby to stop the rise of said liquid.

13. In a device'of the character described, an upper hollow trap member,means separating the interior of said upper trap member into inner andouter communicating chambers, said upper trap member having a topopening to the outer chamber and removable means closingv the opening,said upper trap separating means having a top opening substantially inaxial alignment with the top opening in the upper trap member and aremovable closure member restricting flow between said inner and outerchambers through said separating means, said upper trap member innerchamber also having a bottom opening substantially in axial alignmentwith its top opening, a lower hollow trap member disposed at arelatively fixed distance from the upper trap member, means separatingthe lower trap member into inner and outer communicating chambers, saidlower trap member having a top opening to its inner chamber and in axialalignment with the-said bottom opening in the upper trap member, and atubular sight glass extending between said upper and lower trap membersand through its respective ends establishing communication between theinner chambers oi the upper and lower trap members respectively throughthe bottom and top openings thereof, said sight glass being insertableand removable through the top openings of said upper trap member and thesaid separating means in the upper trap member.

14. In a device of the character described, an

upper hollow trap member, means separating the interior of said uppertrap member into inner and outer communicating chambers, said upper trapmember having a top opening to the outer chamber and removable meansclosing the opening, said upper trap separating means having a topopening substantially in axial alignment with the top opening in theupper trap member and a removable closure member restricting iiowbetween said inner and outer chambers through said separating means,said upper trap member inner chamber also having a bottom openingsubstantially in axial alignment with its top opening, a lower hollowtrap member disposed at a relatively iixed distance from the upper trapmember, means separating the lower trap member into inner and outerchambers communicating with each other at their lower portions, saidlower trap member having a top opening to said inner chamber and inaxial alignment with the said bottom opening in the upper trap member, atubular sight glass extending between said upper and lower trap membersand through its respective ends establishing communication between theinner chambers of the upper and lower trap members, said sight glassbeing insertable and removable through the top openings ci said uppertrap member and the said separating means in the upper trap member, aliquid displacement member removably disposed in the inner chamber ofsaid lower trap member, and a valve, adapted to float upon a liquid,freely supported by said displacement member whereby upon apredetermined rise of liquid in the inner chamber of the lower trapmember the valve will iloat off of its support and close the top openingin the lower trap member.

15. In a device of the character described, an upper trap member havingaligned top and bottom openings, a tubular partition in said upper traymember and substantially concentrically disposed about said bottomopening, the top of said partition being spaced from the top of theupper trap member, removable means having a restricted aperturetherethrough providing a closure for the top of said partition, a lowertrap member having a top opening aligned with the bottom opening of theupper trap member, a sight glass extending between said trap members andinto the bottom opening of the upper member at one of its ends and intothe top opening of said. lower member at the other of its ends, saidupper and lower members being disposed in substantially xed positionsrelative to one another,

said sight glass being insertable and removable through the top openingin the upper member, means for sealing the junctures between said sightglass and upper and lower traps, and removable means normally closingthe top opening in the upper member.

16. In a device of the character described, an upper trap member havingaligned top and bottom openings, a lower trap member having a topopening aligned with the bottom opening of the upper trap member, asubstantially cylindrical partition in said upper trap member dividingthe trap into two chambers one of which substantially surrounds theother, said partition having a top opening providing a passagetherethrough for the fiow of fluid from one chamber to the other andsaid partition top opening being aligned with said openings in saidupper trap member, removable means for restricting the free flow offluid from one of said chambers to the other through said passage, asight glass extending between said trap members and into the bottomopening of the upper member at one of its ends and into the top openingof said lower member at the other of its ends, said upper and lowermembers being disposed in substantially xed positions relative to oneanother, said sight glass being insertable and removable through the topopening in the upper member, means for sealing the junctures betweensaid sight glass and upper and lower traps, and removable means normallyclosing the top opening in the upper member.

1'7. In a remote liquid level indicator, an indicating tube, a trapchamber casing connecting to the lower end thereof, leaving asubstantial portion of the tube unobstructed, a partition member in saidcasing dividing it into primary and secondary chambers,intercommunicating at their lower ends, the indicating tube beingconnected to the primary chamber, a water conduit adapted to extend froma receptacle to be measured and connected to the trap chamber casing andcommunicating with the secondary chamber, a body of water in saidconduit extending partially into the secondary chamber, a body ofmercury below the body of water, said mercury occupying the remainder ofthe secondary chamber and a portion of the primary chamber to a placeabove the normal level of intercommunication between said chambers, abody of liquid nonmiscible with mercury located within the indicatingtube and the remainder of the primary chamber and iioating upon themercury therein, the opening from the primary chamber into theindicating tube providing a valve seat, a valve element capable offloating on mercury but not in the liquid thereabove, means forsupporting the valve element independently of the mercury and injuxtaposition to the opening into the indicating tube whereby, in theevent of breakage of the indicating tube with a consequent rise in thelevel of mercury within the primary compartment due to the pressure ofliquid in the conduit connected with the secondary chamber, the valveelement will be lifted by the mercury and brought into position closingsaid opening and preventing flow of mercury out of the primary chamber,said valve supporting means having a passage therethrough forestablishing communication between the primary chamber above the maximumnormal level of the mercury therein and the exterior of said trapcasing, and means normally closing said passage.

18. A liquid level indicator comprising, a trap chamber casing, apartition in the trap chamber separating it into primary and secondarychambers, there being a passage providing intercommunication betweenlower portions of said chambers, the primary chamber being arranged forconnection with an indicating tube, the secondary chamber being arrangedfor connection with a water conduit adapted to cause head pressure inthe conduit to be imposed on the trap chambers, said trap chamber casingbeing adapted to contain a body of heavy liquid extending into both theprimary and secondary chambers and adapted to contain a body of lighterliquid, nonmiscible with the heavier liquid, disposed in the primarychamber, said casing having an opening in its lower end, means forwithdrawing a portion of the lighter liquid from the primary chamber,said means comprising a pin-like element disposed in the primary chamberfunctioning properly to proportion the volume of the primary chamberwith that of the secondary chamber, said element being removable throughsaid opening, means for securing. said pin-like element to they casing,said pin-like element being formed with aY duct extending. therethrough,and means for closing the duct.

i9. A remote liquid level indicator of the type in whichV two superposedcolumns. of nonmiscible liquids, each diiering from the other in itsspecific gravity, are influenced by water contained in Water conduitsconnected respectively above and below the points of normal maximum andminimum levels, said indicator comprising, in combination, a transparentindicating tube, a vertically disposed trap chamber easing havingprimary and secondary chambers communicating with each other at theirlower ends, the indicating tube being directly connected to the upperend of the primary chamber, a water conduit connected to the upper endof. the secondary chamber, said water conduit extending vertically abovethe point of maximum indication to be given by the indicating tube, abody of high specific gravity liquid partially filling. the primary andVsecondary chambers, an indicating uid in the said indicating tube andoating. in the upper porti-on of said primary chamber upon said highspecific gravity liquid, and meansr for bleeding out from said primarychamber, without disturbing said high specific gravity liquid, anyexcess quantity of the indicating uid forv the purpose described.

20. An article of manufacture for use in a liquid level indicator of thecharacter described having a trap chamber casing adapted to contain abody of heavy liquid and adapted to contain a body of lighter liquid,nonmiscible with the heavier liquid, disposed above the heavy liquid,means for withdrawing a portion of the lighter liquid from above theheavy liquid and without disturbing the latter comprising, a pinlikeelement adapted to project into the casing to a place above the normallevel of the heavy liquid, means for securing said pin-like element tothe casing', said pin-like element having a duct extending therethroughfrom a place above the normal level of the heavy liquid to the eX-terior of the casing, and means for closing the duct.

21. An article of manufacture for use in a liquid level indicator of thecharacter described having atrap chamber casing adapted toV contain abody of heavy liquid and adapted tocontainl aV bodyA of lighter liquid,nonmiscible with the heavier liquid, disposed above the heavy liquid,means for withdrawing ak portion of the lighter liquid from above theheavy liquid and without disturbing the latter comprising, a piniikeelement of a length suicient to extend into said casing throughapre-formed opening in the casing and to a place above the normal levelvof the heavy liquid, said element having a duct therethrough extendingfrom a place above the normal level` of the heavy liquid toa placeexterior of the casing, said duct being so formed as to have a risingportion whereby to trap some of the lighter liquid between its ends andabove the heavier liquid tending to flowout of said duct.

FREDERIC MCNEILL.

